Box-shaped central portion of metal aircraft wing



L. STAIGER Sept. 8, 1931.

BOX SHAPED CENTRAL PORTION OF METAL AIRCRAFT WING Filed April 25, 1927Patented Sept. 8, 1931 PATENT OFFICE LUD'WIG STAIGER, OF SPANDAU, NEARBERLIN, GERMANY, ASSIGNOR TO THE FIRM:

' ROHRBACH METALL-FLUGZEUGBAU, G. M. B. 3., OF BERLIN, GERMANYBOX-SHAPED bENTRAL PORTION OF METAL AIRCRAFT WING Application fliedApril 25, 1927, Serial Rb. 186,224. and in Germany Kay 4, 1926.

Metal aircraft wings tri-partite in the direction of flight andincluding a box-shaped central portion with re-inforced base, are wellknown in the art. The flush outer skin of said central portion, attachedto the griders of the interconnected longitudinal webs and transverseties are re-inforced, in the panels between thc girders, by riveted onprofiles arranged parallel to the longitudinal webs along the innersurfaces of the skin and passing through lightening holes in girders ofthe transverse ties, the profiles being of their girders. This newfeature has the advantage of avoiding any reduction of strength in thegirders of the transverse ties, which, therefore, can be economicallymanufactured at and receive a more efiicient shape. \Vith this form ofconstruction one succeeds in completely avoiding the hitherto prevailinginconveniences and difficulties in the assembly of profiles andtransverse ties. resulting in considerable saving of time. Instead ofthe elongated profiles, which are being expensive in manufacture and ofbulky structure, cheaper and more handy sections can be used. Moreoverfrom a statical point of View this form of construction has many markedadvantages. The re-inforcing profiles arranged in the direction offlight efficiently protect the box-angles against bending and torsionstresses, at the same time supporting the longitudinal webs, to thegirders of which they are attached.

The structure of the box can be considerably simplified by arranging there-inforcing webs of one-skin, and preferably of the bottom skin, at theoutside of this skin. The box can then be assembled, after havingcovered the frame work of longitudinal webs and transverse ties with thetop skin, by riveting the inner profiles to the top skin and /or thegirders of the longitudinal webs, afterwards attaching the bottom skin,

which may have already been provided with profiles on its outside. Inall cases the rivet seams can be made without any difliculty, as the boxpermits of easy access from the bottom side, thus facilitating work atthe top skin, whereas the outside arranged webs profiles of the bottomskin onl necessitate the driving in of rivets arrange at the girders ofthe longitudinal webs.

In the drawings is shown, by way of example, a form embodyingconstruction of the subject matter of the present invention.

Fig. 1 shows the box-shaped central portion, in side elevation.

Fig. 2 is a section on the line AB of Fig. 1.

Fig. 3 represents longitudinal web in plan view which has not yet beencovered with a skin.

Fig. 4 is a section on the line CD of Fig. 1 on an enlarged scale.

Fig. 5 is a section on the line EF of Fig. 4. Fig. 6 shows part of thebottom skin of the Win Fig. 7 represents a transverse tie.

Fig. 8 is a detailed part, shown in perspective.

The boa-shaped central portion, to which leadingand trailing edges arehingedly attached and which impart the final sectional form to the wing,consists of two lateral longitudinal webs a, interconnected b transverseties arranged at intervals. he web elements are in skeleton form andthey as well as transverse ties are provided with girders or angledelements or bars 6, d, to which the flush topand bottom skins e, f, areattached, forming a hollow body comprising longitudinal spars, crossconnections and skins or covers of eiiicient bending and torsionalstrength.

The well known practice of re-inforcing the skin panels between thegirders d, 0, 1s improved, according to this invention, by usingprofiles g, h, running parallel to the transverse ties b and attached tothe Web girders a, and of which the former are of C- shaped section andriveted on the inside of the top skin e, whereas the latter, havinganA-shaped section, are arranged on the outside of the bottom skin of thewing. The profiles h, of streamlined section, are provided with asufiiciently large riveting border even at their frontal ends, and arepressed or the like into the section shown in such manner, that the endparts of the pressed parts, completely covering up the profile opening,gradually merge into the end-borders, to which the web girders areriveted.

Assembly of the central portion is as follows: top skin 6 being rivetedon the framework of longitudinal webs a and transverse ties b, theprofiles g are attached to the inside of the skin and the girders c,which presents no difficulty, as all places where rivets must be made,are easily accessible owing to the missing bottom skin. Then the bottomskin f, having already been provided with outside profiles h, isattached, so that only the riveting thereof to the fully accessiblegirders 0 remains. This new manner of arranging the profiles mostperfectly retains the convex form of the skin, since all deformationsare limited to the small length between any two re-inforcing profiles.

Special reasons, as for instance, obtaining a top skin which may bewalked upon safely, may result in arranging the profiles h, incontradistinction to the described manner, on the top skin, and theprofiles g on the inner side of the bottom skin. It is clear that topskin as well as bottom skin may be provided without outside profiles h.

A practice comparing favourably with those hitherto adopted, providesopen profiles and the represented C-profile preferably, on the inside ofboth skins. An open structure is thereby obtained, such as all seaplaneconstructors aspire to obtain, with a view to facilitate inspection andthus avoiding corrosion. Compared with this most vital feature, thesomewhat difiicult assembly of the box is absolutely without importance.

The transverse ties b, the efi'iciency of whose girders had beenconsiderably impaired by the intermediate profiles of the priorpractice, after the adoption of the new practice consist onl of simplethin plates, re-inforced b vertical bars 11, which plates preferably sould be provided with lightening holes is and flanges m at the edges ofthe lightening holes. The girders d, continuous and unimpaired, may beformed by a flange n of the plate. In this case it is to be recommendedto re-inforce said girders by an outside profile h (Fig. 5),'whichparticularly should be used, when local stresses are prevailing,occasioned for example by landing-gear attachments, engine nacelles etc.

It has proved of advantage to re-inforce the skin panels also in wingspan direction, this being done, for instance, by means of metal bandsor strips 0 arranged vertically on the inner side of the skin. Thosebands or strips can be formed according to a well known practice, byflanges of overlapping skin connections p, holding together two or moreskin runs arranged at a stretch in the direction of flight and extendingin win span direction over several transverse ties If, for any reason,it does not seem desirable to flange the edge of some skin run, asection similar to that indicated in Fig. 2 may be riveted on theconnecting seam. This bar 9 is used, when the skin is not provided witha scam in wing span direction, as represented in Fig. 2, to the left.The rc-inforcing memhere 0, g are arranged between the continuousre-inforcing profiles g, h, if both are attached to the same side of theskin, as shown in Fig. 2. Their effect is considerably increased if theyextend continuously, and uninterruptedly cross the profiles arranged atthe o positeside of the skin, as shown, by way 0 example, in the bottomskin according to Figs. 4 and 5. The resulting crossanember frame is ofperfect strength and resistance.

The invention can be applied with equal advantage tohollow box girderswith three or more longitudinal webs. It is of no consequence whetherthe connection of the remaining re-inforcing profiles, which ma beshaped according to requirements, wit the wing skin is effected by meansof screwing, welding or thelikc, instead of riveting. 1n the same mannerthe invention could be applied to the lateral and horizontal controlsurfaces, as same consist of rudder and bipartite fin, the leading ed eof which latter is designed to be detachable.

What I claim is:

1. A metallic box girder wing structure for airplanes including spacedlongitudinal spars of sufiicient depth to give the required wingthickness, and adapted substantially to solely transmit the verticalbending forces, cross ties rigidly bracing said spars, thin and smoothcover plates extending over several cross ties and lying fiat againstand fastened rigidly and directly to both the s are and the cross tiesto form a rigid part ta ring up tensile stresses of the box girder, theskin panels defined by the s are and cross ties being provided with, stiening profiles extending to and lying transverse to the spars, andrigidly fixed to the cover plates, said profiles being adapted totransmit the compression force components of transverse forces from onelongitudinal spar to the other.

2. A metallic box girder wing structure for airplanes including spacedlongitudinal spars of sufiicient depth to give the required wingthickness, and adapted substantially to solely transmit the verticalbending force, cross ties rigidly bracing said spars, thin and smoothcover plates extending over several cross ties and lying fiat againstand fastened rigidly and directly to both the spars and thecross ties toform a rigid part taking up tensile stresses of the box girder, and

the skin panels defined by the spars and cross ties being provided withstiffening profiles extending to and lying transverse to the spars, andrigidly fixed to the profiles, said panels being firmly connected attheir ends to the spars, the cross reenforcing profiles being adapted totransmit the compression force components of transverse forces from onelongitudinal girder into the other.

3. An aircraft wing including a box base, said box consisting ofvertical spars, spaced from each other and rigidly connected and bracedby cross ties which are also spaced from each other, the top and bottomof the box being covered by a thin and smooth skin which is rigidlyconnected with the spars and cross ties in a manner to participate inthe transmission of compression force componcnts of the box base, theskin panels defined by the spars and the cross ties being provided withstiffening rofiles firmly fixed thereon, and extending in the directionof flight, said profiles being firmly connected at their ends to thespars, and adapted to transmit the compression force components oftransverse forces from one longitudinal girder onto the other.

4. An aircraft wing including a boxshaped base and edge parts joinedthereto, said edge parts completing the wing section, said box composedof longitudinal spars spaced from each other, cross ties connecting thespars and smooth upper and lower skin cover plates participating in thetransmission of forces, the cross ties being spaced a certain distancefrom each other, the spars and cross ties having girder flanges attachedthereto and the upper and lower skin plates being fixed to theseflanges, said skin plates essentially transmitting only the compressionforce components of tnansvcrse forces, panels defined by thelongitudinal spars and transverse ties profiles fixed on the skin panelsand nnctioning to stiffen the stressed skin structure, said profilesextending transverse to the spars and being connected at their ends tothe flanges of the spars, and arranged to transmit the compression forcecomponents of transverse forces from one longitudinal girder to theother.

5. In an aircraft wing, a hollow box girder constituting the centralportion thereof, the box consisting of two lateral girders arran ed adistance from each other and inclu ing smooth upper and lower skinplates fixed to the lateral girders, said upper and lower skin forming arigid part of the box and transmitting essentially solely thecompression force components of transverse forces, cross ties arrangedwithin the box a certain distance from each other and rigidly connectedwith both the lateral girders and the smooth skins, strengthening barsconnected to the skins and extending from the front lateral bearer tothe rear lateral bearer and being fixed to both bearers, said bars beingadapted to transmit the compression force components of transverseforces from one lateral girder onto the other.

6. A hollow box girder constituting the base structure of an aircraftwing, the box including lateral spars and smooth upper and lower skinplates rigidly connected thereto. said upper and lower skin platestransmitting essentially solely the compression force components oftransversely acting forces, cross ties arranged within the box a certaindistance from each other, the cross ties being connected with the sparsand the skins, stiffening bars rigidly connected to the skins, the barsbeing located in the direction of flight between the cross tics andbeing connected also with the spars, said bars being adapted to transmitthe compression force components of transverse forces from one lateralspar to the other, the bars of one skin being located on the inner sideof the skin, the bars of the other skin being located on the outer sideof the skin.

7. A hollow box girder according to claim 6, wherein the stifi'cningbars of the upper skin are located on the inner side of the skin, thebars of the lower skin being located on the outer side of the skin.

8. A hollow box girder constituting the foundation of an aircraft wing,the box including lateral spars and smooth upper and lower skin platesrigidly connected thereto, said upper and lower skin plates transmittingessentially solely the compression force components of transverse actionof the box, cross ties arranged within the box a certain distance fromeach other, the cross ties being rigidly connected with both the sparsand the skins, stiffening bars fixed to the skins, the bars beinglocated in the direction of flight between the cross ties and connectedwith the spars, two or more bars being located within the box space,said bars being adapted to transmit the compression force components oftransverse forces from one lateral spar to the other, said barsconsisting of sections which are free at one longitudinal edge aftertheir fixation.

9. A hollow box girder according to claim 8, the open sections beingC-shaped profiles with flanges or girders of unequal width, the largerone being against the skin.

10. A hollow box girder constituting the base structure of an aircraftwing, the box including lateral spars and upper and lower skin platesconnected thereto. said upper and lower skin plates participating in thetransmission of forces oi the box, cross ties arranged within the box acertain distance from each other, said cross ties be ng connected withboth the spars and the skins, stiffening bars being fixed to the skinsand located in the direction of flight between the cross ties and alsoconnected with the spars, certain of the stiflening bars being locatedon the outer side of the box skins, said exterior bars consisting of ahollow section and havin their ends stream-lined and formed into lateraledges bent 011' the hollow section, said edges serving for fixing thesti fl'ening sections to the box wall.

11. A hollow box girder according to claim 10, wherein hollow profilesare also arranged in the plane of the cross ties.

12. A hollow box girder constituting the base structure of an aircraftwing, the box including lateral sp'ars and smooth upper and lower Sklnplates connected thereto, said up-' per and lower skin platesparticipating in the transmission of forces of the box, cross tiesarranged within the box a certain distance from each other, said crossties being connected with the spars and the skins, stiffening bars fixedto the skins, the bars being located in the direction of flight betweenthe cross ties andbeing connected with the spars, the skins beingprovided with connections which ruri in the direction of the wing span,the edge of the skin being bent round at a right angle at certain placesof connection, said flan es being located on one side of the skin, t estiffening bars which are fixed separately and run in the direction ,offlliight, being located on the other side of the s in.

13. A hollow box girder constituting the base structure of an aircraftwing, the box including lateral spars and upper and lower skin platesconnected thereto, said upper and lower skin lates being smooth andparticipating in the transmission of forces of the box, cross tiesarranged within the box seer-- tain distance from each other, said crossties being connected with both the s arc and the skins, stiffening barsfixed to t e skins, the bars being located in the direction of flightbetween the cross ties and being connected with the spars, thelongitudinal walls and cross ties forming skin anels, the skin anels atthe wing end a jacent the fuse a being formed' by one sheet panel, theskin panels of the wing central portion being formed by two skinslocated one behind the o her in the direction of flight and each of themextending over several cross ties.

14. A hollow box girder according to claim 13 wherein the skin panels ofthe wing tip consist of three skins located one behind the other in thedirection of flight and each of them extending over several cross ties.

15. A hollow box girder constituting the base structure of an aircraftwing, the box including lateral longrons and upper and lower skin platesconnected thereto, said upper and lower skin plates being smooth andparticipating in the transmission of forces of the box, cross tiesarranged within the box a certain distance from each other, said crossties being connected with the spars and the skins, stifiening bars beingfixed to the skin the bars being located in the direction 0 flightbetween the cross ties and being connected with the spars, certain ofsaid cross ties consisting of a sheet panel with the upper and loweredge being reinforced by flanges, these sheet panels havin grooves withflanged edges, stiffening mem rs being fixed on the sheet panels, saidstiffening members being substantially vertical and being connected withthe flanges of the said top and bottom edge.

16. A box-shaped central portion of a metal aircraft win formed of threeparts in the direction of flight, said central ortion including twolateral longitudinal we s, and consisting of cross walls which connectthe longitudinal webs with each other and are arranged a certaindistance fromeach other, and also including smooth upper and lower skinplates which are connected to the longitudinal webs and to the crossties and articipates in the transmission of forces 0 the box, the upperand lower skin plates being provided with stifl'ening members, saidmembers being located in the direction of fli ht between the cross tiesand being connecte to the two longitudinal webs, the stiffening membersof at least one of the skins being located on the inner side of theskin.

17. A box-shaped central ortion of a metal aircraft wing formed of t recparts in the direction of flight; said central portidn including twolateral longitudinal webs, cross walls which connect the longitudinalwebs with each other and are arranged a certain distance from eachother, and smooth upper and lower skin plates which are connected to thelongitudinal webs and to thecross ties and participate in thetransmission of forces of the box, the u I per skin being provided onits inner side an the lower skin on its outer side with stifieningmembers, said members being lodated in the direction of flight betweenthe cross ties and being connected to the two longitudinal webs.

18. A box-shaped central ortion according to claim 17, the inner stiening members consisting of opexrC-shaped sections, the exteriorstitfening members consisting of open sections with edges which ,areflanged all round, said edges serving for connecting the sections to theskin, the fixed sections forming with the skin closed profiles.

19. A box-shaped base structure according to claim 1, the wing beingreinforced at the root.

20. A box-(girder construction for aircraft wings inclu i plates andreinforcing members extending in the fore and aft direction attached tosaid plates of A-section and having their ends stream-lined, with themarginal edges formed into securing flanges lying flat against theplates.

ng stressed metal covering- 21. A box-shaped central member for usebetween the front and rear members of a tripartite metal aircraft wing,having a smooth outer skin which is attached to the 5 girders ofinterconnected longitudinal webs and transverse ties and is reinforced,in the panels between the girder members, by means of'profile bars,the'reinforcing profile bars being parallel with the transverse ties and10 having their ends attached to the longitudinal Webs of their girdermembers.

In testimony whereof, I have signed my name to this specification.

15 LUDWIG STAIGER.

21. A box-shaped central member for use between the front and rearmembers of a tripartite metal aircraft wing, having a smooth outer skinwhich is attached to the girders of interconnected longitudinal webs andtransverse ties and is reinforced, in the panels between the girdermembers, b means of profile bars, the reinforcing pro le bars beingparallel with the transverse ties and having their ends attached to thelongitudinal webs of their girder members.

In testimony whereof, I have signed my name to this specification.

LUDWIG STAIGER.

CERTIFICATE OF CORRECTION.

Patent No. 1,822, 247. Granted September 8, 1931, to

LUDWIG STAIGER.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1,line 30, strike out the word "being"; page 2,- line 33, for "without"read with, and line 72, after "section" insert bar q; page 3, line 42,claim 4, before "panels" insert the word skin; page 5, line 11, claim21, for "of" read or; and that the said Letters Patent should be readwith these corrections therein that the same may conform to the recordof the ease in the Patent Office.

Signed and sealed this 27th day of October, A. D. 1931.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,822,247. Granted September 8, 1931, to

LUDWIG STAIGER.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1.line 30, strike out the word "being"; page 2,' line 33, for "without"read with, and line 72, after "section" insert bar 1 page 3, line 42.claim 4, before "panels" insert the word skin; page 5, line 11, claim21. for "of" read or; and that the said Letters Patent should be readwith these corrections therein that the same may conform to the recordof the case in the Patent Office.

Signed and sealed this 27th day of October, A. D. 1931. n

M. J. Moore. 1 (Seal) Acting Commissioner of Patents.

